Helen FieldsScience Writer

Tonight I went on a tour of the fossil labs at the Smithsonian’s National Museum of Natural History, organized by the DC Science Writer’s Association. I learned many exciting things and took pictures with my cell phone camera, ’cause that’s all I had. Sorry.

Sample fun fact: When they find little fossils in the field, they wrap them up in toilet paper and tape.

I like the one that says “Chunk-o-Bone.” And the other one that says “Bone?” Might be a bone. Might not. We also learned that you can sometimes tell the difference between bone and petrified plant material by licking it – bone is porous, so it wicks liquid away from your tongue and your tongue sticks to it. Petrified wood is solid and doesn’t do that. (Unfortunately, I didn’t get a picture of this demonstration.)

We learned a lot about preparing fossils. When fossils come back from the field, they’re often stuck in rock. So, you want to cut away the rock. The preparators have jackhammers as small as a dentist’s drill. Some rock is just too hard for chipping away, though. These vats are for dissolving fossils in acid:

These fossils are in limestone, which apparently is really hard. If you chipped bits of it away, it would take forever. So instead they bathe them in really weak acetic acid, over and over and over and over. After every overnight bath, someone has to coat the bones with a plastic solution so the acid won’t dissolve them, too. With weekly baths, dissolving the bones out of a rock takes…forever. Like a year. Acid won’t dissolve plant fossils, so if that’s what you’re trying to get out of the rock, you can just throw in the rocks, put mesh over the drain, add some super-strong acid, and wait.

The vertebrate paleontology folks are in the process of making custom-fit foam and plaster jackets for all their fossils. Big fossils are heavy. REALLY heavy. They’re basically rocks, and think how big a dinosaur leg bone is – that’s a big rock. Until someone dug them up, these fossils were happily ensconced in some kind of rock formation. So if you have a big old bone sitting on a shelf, and it’s just resting on three or so points, it’s really likely to break. Here’s a fossil getting its cast made:

The sand supports the weight of the fossil while it’s being worked on. My favorite fact: That sand is made of crushed garnets. It’s cleaner than regular sand, apparently. Also, red. And so pretty!

Our last stop was in a big room with big stuff. Example: That white thing in the back is a fossil branch of some kind of ancient tree fern. It’s so big, for years it leaned against the wall outside in the parking lot. They were afraid it would break the floor if they brought it inside. Note that it is inside now. They cut a lot of rock off the back before they brought it in.

At left is some dinosaur whose name I’ve forgotten. This is actually a cast; the original has been on display, but they’re trying to take their type specimens down. (I think he said there are seven in the dinosaur hall right now.) A type specimen is the specimen that defines a species, so paleontologists want to be able to study them. The museum is replacing them with casts so scientists can work with the type specimens.

The Natural History has redone two of its major halls recently – mammals and oceans – and a third is opening this spring. The dinosaur hall is next on the list. Apparently a lot of the skeletons are mounted based on antiquated ideas about how dinosaurs stood. Some date to shortly after the museum opened – which was in 1910. So if you know anyone with a few million dollars to throw around, the Smithsonian would love to hear from them.

UPDATE, 2/1/10: Here’s some more info about that giant tree fossil. It was a “scale tree” and it came from a coal mine in Iowa. The museum received it in 2005.

For all my Museum Tourist posts, click here.

photos: me.